The present invention relates to a deflectable element for transmitting pushing and pulling forces as well as torque having a straight configuration and a bent configuration and to a medical instrument comprising such an element.
In medical instruments and in particular in medical instruments for endoscopic surgery it is often necessary to transmit pushing and pulling forces via an actuating element for example from a handle arranged at a proximal end of a medical instrument to a tool or a set of tools at a distal end of the instrument for example in order to open and close the tool. It is often also desirable to transmit torque in order to rotate the tool.
Furthermore the tool is often deflectable relative to the shaft, in which case the instrument must be designed so that the pushing and pulling forces as well as torque can be transmitted both in the deflected and the non-deflected state of the tool.
An element for transmitting torque while in a non-straight configuration is for example known from U.S. Pat. No. 5,214,970. The element disclosed therein comprises a base plate and an end plate and a set of bellows arranged between the base plate and the end plate. Arranged within the set of bellows is a spring which pushes the end plate away from the base plate. Furthermore the element known from this document comprises a wire connecting the base plate to the end plate and limiting the distance by which the base plate and the end plate can be separated from each other.
Although it has been shown that such an element is able to effectively transmit torque as well as, to a certain degree, pulling forces, it has been shown that the transmission of pushing forces using such an element is problematic. If the spring within the element is strong enough to effectively transmit pushing forces it is generally not flexible enough for the element to be bent to any useful degree. If the spring is sufficiently elastic so that the element can be bent to a useful degree, the spring is usually too elastic to transmit pushing forces in any meaningful way or if it does it tends to do so such that the applied forces are transmitted in a non-linear way which is also not desirable.